1. Field of the Invention
This invention relates to orthopaedic splint type devices for the hand used to align the proximal phalanges when necessary because of ulnar drift.
2. Description of the Prior Art
Rheumatoid arthritis is an incurable disease which affects a large number of individuals to varying degrees. In severe cases, the disease is both painful and crippling. Due to the incapacitive nature of the disease, various adaptive equipment and splints exist in the prior art to assist individuals in dealing with the effects of this disease.
When the hands become involved in the arthritic disease process, internal forces in the hand and fingers change due to pain, inflammation and swelling. This creates dynamic and static imbalances which result in deformities. Specifically, as the tendons and ligaments around the joint become over stretched and the bone structure of the joint deteriorates due to the disease, the joints become very unstable in all directions through the full range of flexion and extension. Chronic pain and general muscle weakness exacerbate the problem of joint instability to the point of serious loss of function in the rheumatoid hand.
When joint instability occurs in the lateral plane, it frequently results in ulnar deviation of the fingers at the metacarpophalangeal joints (ulnar drift). Specifically, ulnar drift results from the degradation due to disease or injury of the structures holding the flexor and/or extensor tendons in normal placement. Following this degradation, the tendons slip from their normal position toward the ulnar side of the hand. During normal grasp and release hand movement, the displaced tendons exert a lateral torque in the ulnar direction about the metacarpophalangeal joints, which results in ulnar medial deviation or ulnar drift of the phalanges. Ulnar drift causes decreased prehension, loss of grip strength and unacceptable cosmesis.
Furthermore, when ulnar drift occurs, the head of the second metacarpal bone of the index finger usually protrudes due to atrophy of the interosseous muscle. This bony protrusion must be avoided on the radial side of the hand when splinting, because it is painful when splints and/or straps rest on the protrusion and skin breakdown frequently occurs.
Prior art splints have attempted to address the problem of ulnar drift. They are typically palmar or dorsal hand based splints with padding and finger separators, such as disclosed in Barber, "Ulnar Deviation Splint," U.S. Pat. No. 4,558,694. The '694 patent, from the user's standpoint, has many drawbacks to the disclosed device. The use of hook and loop material requires more physical grip strength than many arthritis patients have in their fingers. Further the finger separators maintain the user's fingers in an abducted (separated) position which is awkward for performing normal everyday activities. Furthermore, the straps of the device simply hold the hand in relation to itself. There are no other areas of the hand or arm which are used to stabilize the hand and prevent ulnar drift. Prior to the Barber patent, Czap, "Ulnar Drift Splint," U.S. Pat. No. 3,299,887, in fact suggests a hinged mechanism to support laterally deviating fingers. Unfortunately, these prior art splints fail to provide sufficient leverage to correct ulnar drift.
As discussed above, when ulnar drift occurs, the fingers deviate in a lateral plane, with the axis of deviation being at the metacarpophalangeal joints. To correct this deformity, the splint needs to contact the affected area in three distinct and sufficiently separate areas to allow corrective leverage.
Palmar and dorsal hand based splints of the prior art are short, rotating when ulnarly deviating fingers push against the distal end of the splint. As the splint rotates, the distal edge on the radial side of the splint digs into the neck of the metacarpal bone just proximal to the head. This area is frequently recessed due to atrophy of the interosseous muscle, and it is very painful to have a splint either digging in proximal to the head of the metacarpal bone or resting directly on the lateral side of the metacarpal joint. Furthermore, splints resting on, and/or digging into, this area causes pressure sores and skin breakdown. Additionally, prior art splints tend to be bulky, abduct (spread apart) the fingers and have straps which make donning and doffing the splint difficult for individuals with limited hand function and grip strength. The ulnar support splint of the present invention overcomes the deficiencies of the prior art by providing a splint of sufficient overall length to provide corrective forces in the lateral plane.